/**
 * 2008-6-16
 */
package com.fcy.security.dh;

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.PrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * DH安全编码组件
 * 
 * @author 梁栋
 * @version 1.0
 */
public abstract class DHCoder {

	/**
	 * 非对称加密密钥算法
	 */
	public static final String KEY_ALGORITHM = "DH";

	/**
	 * 本地密钥算法，即对称加密密钥算法，可选DES、DESede和AES算法
	 */
	public static final String SECRET_KEY_ALGORITHM = "AES";

	/**
	 * 默认密钥长度
	 * 
	 * DH算法默认密钥长度为1024 密钥长度必须是64的倍数，其范围在512到1024位之间。
	 */
	private static final int KEY_SIZE = 512;

	/**
	 * 公钥
	 */
	private static final String PUBLIC_KEY = "DHPublicKey";

	/**
	 * 私钥
	 */
	private static final String PRIVATE_KEY = "DHPrivateKey";

	/**
	 * 初始化甲方密钥
	 * 
	 * @return Map 甲方密钥Map
	 * @throws Exception
	 */
	public static Map<String, Object> initKey() throws Exception {

		// 实例化密钥对生成器
		KeyPairGenerator keyPairGenerator = KeyPairGenerator
				.getInstance(KEY_ALGORITHM);

		// 初始化密钥对生成器
		keyPairGenerator.initialize(KEY_SIZE);

		// 生成密钥对
		KeyPair keyPair = keyPairGenerator.generateKeyPair();

		// 甲方公钥
		DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

		// 甲方私钥
		DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

		// 将密钥对存储在Map中
		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);

		return keyMap;
	}

	/**
	 * 初始化乙方密钥
	 * 
	 * @param key
	 *            甲方公钥
	 * @return Map 乙方密钥Map
	 * @throws Exception
	 */
	public static Map<String, Object> initKey(byte[] key) throws Exception {

		// 解析甲方公钥
		// 转换公钥材料
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);

		// 实例化密钥工厂
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

		// 产生公钥
		PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);

		// 由甲方公钥构建乙方密钥
		DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();

		// 实例化密钥对生成器
		KeyPairGenerator keyPairGenerator = KeyPairGenerator
				.getInstance(keyFactory.getAlgorithm());

		// 初始化密钥对生成器
		keyPairGenerator.initialize(dhParamSpec);

		// 产生密钥对
		KeyPair keyPair = keyPairGenerator.genKeyPair();

		// 乙方公钥
		DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

		// 乙方私钥
		DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

		// 将密钥对存储在Map中
		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);

		return keyMap;
	}

	/**
	 * 加密
	 * 
	 * @param data
	 *            待加密数据
	 * @param key
	 *            密钥
	 * @return byte[] 加密数据
	 * @throws Exception
	 */
	public static byte[] encrypt(byte[] data, byte[] key) throws Exception {

		// 生成本地密钥
		SecretKey secretKey = new SecretKeySpec(key, SECRET_KEY_ALGORITHM);

		// 数据加密
		Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());

		cipher.init(Cipher.ENCRYPT_MODE, secretKey);

		return cipher.doFinal(data);
	}

	/**
	 * 解密<br>
	 * 
	 * @param data
	 *            待解密数据
	 * @param key
	 *            密钥
	 * @return byte[] 解密数据
	 * @throws Exception
	 */
	public static byte[] decrypt(byte[] data, byte[] key) throws Exception {

		// 生成本地密钥
		SecretKey secretKey = new SecretKeySpec(key, SECRET_KEY_ALGORITHM);

		// 数据解密
		Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());

		cipher.init(Cipher.DECRYPT_MODE, secretKey);

		return cipher.doFinal(data);
	}

	/**
	 * 构建密钥
	 * 
	 * @param publicKey
	 *            公钥
	 * @param privateKey
	 *            私钥
	 * @return byte[] 本地密钥
	 * @throws Exception
	 */
	public static byte[] getSecretKey(byte[] publicKey, byte[] privateKey)
			throws Exception {

		// 实例化密钥工厂
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

		// 初始化公钥
		// 密钥材料转换
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKey);

		// 产生公钥
		PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);

		// 初始化私钥
		// 密钥材料转换
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(privateKey);

		// 产生私钥
		PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

		// 实例化
		KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory
				.getAlgorithm());

		// 初始化
		keyAgree.init(priKey);

		keyAgree.doPhase(pubKey, true);

		// 生成本地密钥
		SecretKey secretKey = keyAgree.generateSecret(SECRET_KEY_ALGORITHM);

		return secretKey.getEncoded();
	}

	/**
	 * 取得私钥
	 * 
	 * @param keyMap
	 *            密钥Map
	 * @return byte[] 私钥
	 * @throws Exception
	 */
	public static byte[] getPrivateKey(Map<String, Object> keyMap)
			throws Exception {

		Key key = (Key) keyMap.get(PRIVATE_KEY);

		return key.getEncoded();
	}

	/**
	 * 取得公钥
	 * 
	 * @param keyMap
	 *            密钥Map
	 * @return byte[] 公钥
	 * @throws Exception
	 */
	public static byte[] getPublicKey(Map<String, Object> keyMap)
			throws Exception {

		Key key = (Key) keyMap.get(PUBLIC_KEY);

		return key.getEncoded();
	}
}
